Due to high current density, high breakdown voltage, and low ON resistance, High Electron Mobility Transistors (HEMTs) are suitable for use in power applications. An HEMT structure includes a channel layer and an active layer. A two-dimensional electron gas (2DEG) is generated in the channel layer, adjacent an interface with the active layer. The 2DEG is used in the HEMT structure as charge carriers. The 2DEG is generated even in the absence of a voltage applied to the HEMT structure. Thus, an HEMT structure is, by nature, a normally ON structure with a negative threshold voltage. A consideration in designing circuitry for power applications involves converting a normally ON HEMT structure to a normally OFF HEMT structure with a positive threshold voltage.